The use of the aquatic plant cattail to produce an adsorbent for heavy metals will add value to wetlands. Cattail adsorbents were treated with multi-valent carboxylic acids to facilitate adsorption of Pb(II) from a vanillin solution. Fourier transform infrared (FTIR) spectroscopic analysis confirmed the formation of acid modifications by esterification. While unmodified cattail had a Pb(II) adsorption capacity of 3.21 mg/g, citric acid-, malic acid-, tartaric acid-, oxalic acid-, and iminodiacetic acid-modified cattail absorbents were able to adsorb 66.10, 55.42, 44.53, 52.32, and 36.82 mg/g, respectively, at the optimum pH of 4.9. The Pb(II) adsorption capacity increased as the concentration of Pb(II) increased without loss of vanillin during the adsorption process. Desorption of Pb(II) and regeneration of the adsorbents was achieved by 0.1 M HCl elution, which showed that the cattail adsorbents were regenerated easily and could be used repeatedly. The results suggest that acid-modified cattail biomass may be a promising adsorbent for heavy metal ion uptake in water-based cosmetics.